Digital x-ray detector arrays are generally fabricated on a glass substrate having a detector backplane, including an amorphous silicon (a-Si) thin film transistor (TFT) array arrangement, a corresponding a-Si photodiode array arrangement, along with associated metal electrodes and contact lines. An x-ray scintillator is placed in contact with the detector backplane to convert x-rays to light that is detected by the photodiode array arrangement. The scintillator is commonly constructed using Tb-doped gadolinium oxysulphide (GOS) or cesium iodide (CsI), but it is appreciated other materials may also be used. While the GOS scintillator may be bonded to the backplane, more commonly, the GOS scintillator is not bonded to the backplane but instead is pushed into contact therewith. The CsI scintillator may also be deposited and bonded directly on the backplane or alternatively formed as a separate layer and pushed into contact with the backplane. The completed digital x-ray detector includes the glass substrate which results in a substantially rigid device.
In looking to develop more flexible designs, the structures described above can be deposited on a flexible plastic substrate instead of a glass substrate to increase flexibility. However, many of the materials used in the digital x-ray detector structure including a-Si, indium tin oxide (ITO—an oxide semiconductor used to form a photodiode transparent top contact), and CsI are either brittle or fragile and have a tendency to crack under the strain of bending. An exception (among others) is GOS, which is made as powder in a polymeric binder and has a relative amount of flexibility.
As a result transitioning the conventional detector materials and structures from glass to flexible plastic substrates makes them rugged against breakage when dropped, but exposes the detectors to damage when bent.
This is an issue as bendable detectors are of significant interest, for example, in areas of security such as to inspect pipelines or other curved objects, to image objects in confined spaces where a rigid flat detector could not be introduced, and to conform to the human body for added comfort and resolution, among a multitude of other uses. Consequently, it is deemed desirable to engineer flexible detectors that remain robust to bending, as well as when dropped.